The effect of electron donating and withdrawing groups on the morphology and optical properties of Alq3

By adding electron donating (EDG) and withdrawing groups (EWG) to the Tris-(8-hydroxyquinoline) aluminum (Alq3) molecule, the emission color can be tuned. In this study the effect of EDG and EWG on the morphology and optical properties of Alq3 were investigated. Alq3 powders was synthesized with an EDG (–CH3) substituted at positions 5 and 7 ((5,7-dimethyl-8-hydroxyquinoline) aluminum) and EWG (–Cl) at position 5 ((5-chloro-8-hydroxyquinoline) aluminum). A broad absorption band at ~380 nm was observed for Alq3. The bands of the substituted samples were red-shifted. The un-substituted Alq3 showed a high intensity emission peak at 500 nm. The –Cl and –CH3 samples showed a red-shift of 33 and 56 nm respectively. The morphology of the samples was studied using a scanning electron microscope. The photo degradation of the samples was also investigated and the dimethyl sample shows the least degradation to the UV irradiation over the 24 h of continuous irradiation.